# menu_driver 3x

    menu_driver(3x)                                         menu_driver(3x)

## NAME

           menu_driver - command-processing loop of the menu system

## SYNOPSIS

           #include <menu.h>
           int menu_driver(MENU *menu, int c);

## DESCRIPTION

           Once a menu has been posted (displayed), you should funnel
           input events to it through menu_driver.  This routine  has
           three major input cases:

           -  The  input  is  a  form navigation request.  Navigation
              request codes are constants defined in <form.h>,  which
              are distinct from the key- and character codes returned
              by wgetch.

           -  The input is a printable character.  Printable  charac-
              ters  (which  must  be  positive,  less  than  256) are
              checked according to the program's locale settings.

           -  The input is the KEY_MOUSE special key associated  with
              an mouse event.

           The menu driver requests are as follows:

           REQ_LEFT_ITEM
                Move left to an item.

           REQ_RIGHT_ITEM
                Move right to an item.

           REQ_UP_ITEM
                Move up to an item.

           REQ_DOWN_ITEM
                Move down to an item.

           REQ_SCR_ULINE
                Scroll up a line.

           REQ_SCR_DLINE
                Scroll down a line.

           REQ_SCR_DPAGE
                Scroll down a page.

           REQ_SCR_UPAGE
                Scroll up a page.

           REQ_FIRST_ITEM
                Move to the first item.

           REQ_LAST_ITEM
                Move to the last item.

           REQ_NEXT_ITEM
                Move to the next item.

           REQ_PREV_ITEM
                Move to the previous item.

           REQ_TOGGLE_ITEM
                Select/deselect an item.

           REQ_CLEAR_PATTERN
                Clear the menu pattern buffer.

           REQ_BACK_PATTERN
                Delete   the  previous  character  from  the  pattern
                buffer.

           REQ_NEXT_MATCH
                Move to the next item matching the pattern match.

           REQ_PREV_MATCH
                Move to the previous item matching the pattern match.

           If  the second argument is a printable character, the code
           appends it to the pattern buffer and attempts to  move  to
           the  next  item  matching the new pattern.  If there is no
           such match, menu_driver returns E_NO_MATCH and deletes the
           appended character from the buffer.

           If  the  second  argument  is one of the above pre-defined
           requests, the corresponding action is performed.

       MOUSE HANDLING
           If the second argument is the KEY_MOUSE special  key,  the
           associated mouse event is translated into one of the above
           pre-defined requests.  Currently only clicks in  the  user
           window  (e.g.  inside the menu display area or the decora-
           tion window) are handled.

           If you click above the display region of the menu:

                  a REQ_SCR_ULINE is generated for a single click,

                  a REQ_SCR_UPAGE is generated for a double-click and

                  a REQ_FIRST_ITEM is generated for a triple-click.

           If you click below the display region of the menu:

                  a REQ_SCR_DLINE is generated for a single click,

                  a REQ_SCR_DPAGE is generated for a double-click and

                  a REQ_LAST_ITEM is generated for a triple-click.

           If you click at an item inside the  display  area  of  the
           menu:

                  -  the menu cursor is positioned to that item.

                  -  If you double-click an item a REQ_TOGGLE_ITEM is
                     generated  and  E_UNKNOWN_COMMAND  is  returned.
                     This  return value makes sense, because a double
                     click usually means that an item-specific action
                     should  be  returned.  It is exactly the purpose
                     of this return value to signal that an  applica-
                     tion specific command should be executed.

                  -  If  a  translation  into  a  request  was  done,
                     menu_driver returns the result of this  request.

           If  you clicked outside the user window or the mouse event
           could  not  be  translated  into   a   menu   request   an
           E_REQUEST_DENIED is returned.

       APPLICATION-DEFINED COMMANDS
           If the second argument is neither printable nor one of the
           above pre-defined menu requests or  KEY_MOUSE,  the  drive
           assumes  it is an application-specific command and returns
           E_UNKNOWN_COMMAND.  Application-defined commands should be
           defined  relative  to  MAX_COMMAND,  the  maximum value of
           these pre-defined requests.

## RETURN VALUE

           menu_driver return one of the following error codes:

           E_OK The routine succeeded.

           E_SYSTEM_ERROR
                System error occurred (see errno).

           E_BAD_ARGUMENT
                Routine detected an incorrect or  out-of-range  argu-
                ment.

           E_BAD_STATE
                Routine was called from an initialization or termina-
                tion function.

           E_NOT_POSTED
                The menu has not been posted.

           E_UNKNOWN_COMMAND
                The menu driver code saw an unknown request code.

           E_NO_MATCH
                Character failed to match.

           E_REQUEST_DENIED
                The menu driver could not process the request.

## SEE ALSO

           curses(3x), menu(3x), wgetch(3x).

## NOTES

           The header file <menu.h> automatically includes the header
           files <curses.h>.

## PORTABILITY

           These  routines  emulate  the System V menu library.  They
           were not supported on Version 7 or BSD versions. The  sup-
           port for mouse events is ncurses specific.

## AUTHORS

           Juergen  Pfeifer.   Manual  pages  and  adaptation for new
           curses by Eric S. Raymond.

                                                            menu_driver(3x)